Illustrated herein are imaging members, and more specifically, positively and negatively charged electrophotographic imaging members and processes for forming images on the member. More specifically, disclosed herein are layered photoconductive imaging members useful in electrostatic digital, including color, process, and which members contain an optional supporting substrate, a photogenerating layer, a charge transport layer, and an optional protective overcoating layer and wherein the photogenerating layer contains a mixture of a photogenerating pigment, or pigments, an optional polymeric binder, and an electron transport component. In embodiments, the amount of photogenerating pigment and the amount of electron transport selected can each be adjusted to, for example, permit the photosensitivity tuneability of the photogenerating layer. More specifically, in embodiments the amount or concentration of the higher sensitivity photogenerating pigment present in the photogenerating layer can be preselected and varied to, for example, permit a number of different photosensitivities for the imaging members thereof.
Advantages of the imaging members illustrated herein in embodiments include the avoidance of extended milling times of a second photogenerating pigment in the photogenerating layer to thereby avoid/minimize an increase in the dark decay characteristics and maintaining the capacitive charging characteristics at low fields, and wherein the electrical properties of the members are excellent and in some instances improved as compared to similar members without an electron transport in the photogenerating and without adjusting the amount of a photogenerating pigment as illustrated herein. Also, when a blocking layer is present, especially a thick layer of, for example, from about 1 to about 20 microns, there can be achieved a reduction in the residual voltage caused primarily by the diffusion/penetration of the electron transport component from the photogenerating layer into the blocking layer thereby improving the electron mobility of the blocking layer. Moreover, in embodiments when the photogenerating layer contains the electron transport component there is permitted, for example, thicker photogenerating layers while maintaining relatively high pigment concentrations such that much of the light absorption is accomplished at the top, from about 2 to about 5 microns, and which layer may also minimize charge deficient spots and may allow improvements in the preparation of the members and the coating robustness thereof. Also, the presence of an electron transport component in the photogenerating layer can enhance electron mobility and thus enable a thicker photogenerating layer, and which thick layers can be more easily coated than a thin layer, such as about 0.1 to about 2 microns thick.
The imaging members of the present invention in embodiments exhibit excellent cyclic/environmental stability; excellent wear characteristics; extended lifetimes of, for example, up to 1,000,000 imaging cycles; minimum microcracking; elimination/minimization of adverse affects when contacted with a number of solvents such as methylene chloride, tetrahydrofuran and toluene; acceptable and in some instances improved electrical characteristics; excellent imaging member surface properties; and which members can be selected for both drum and belt photoreceptors.
Processes of imaging, especially xerographic imaging, and printing, including digital, are also encompassed by the present invention. More specifically, the photoconductive imaging members of the present invention can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein charged latent images are rendered visible with toner compositions of an appropriate charge polarity. The imaging members are in embodiments sensitive in the wavelength region of, for example, from about 475 to about 950 nanometers, and in particular from about 650 to about 850 nanometers, thus diode lasers can be selected as the light source. Moreover, the imaging members of this invention are useful in color xerographic applications, particularly high-speed color copying and printing processes.